A lithium battery in the related art uses a lithium metal as a negative electrode active material, but when a lithium metal is used, a battery is short-circuited due to formation of dendrite to cause danger of explosion, so that a carbon-based material is widely used as a negative electrode active material, instead of a lithium metal.
The carbon-based active material includes crystalline carbon, such as natural graphite and artificial graphite, and amorphous carbon, such as soft carbon and hard carbon. However, the amorphous carbon has a large capacity, but has a problem in that irreversibility is large during a charging/discharging process. Graphite is representatively used as the crystalline carbon, and has a theatrical limit capacity of 372 mAh/g, which is large, so that graphite is used as a negative electrode active material.
In order to develop a next-generation high capacity lithium battery, a development of a negative electrode active material having a high capacity beyond the capacity of graphite is essentially required. To this end, a material, which is currently and actively researched, is a silicon-based negative electrode active material. The silicon has a high capacity and a high energy density, and is capable of occluding and discharging the larger amount of lithium ions than the negative electrode active material using the carbon-based material, so that it is possible to manufacture a secondary battery having a high capacity and a high energy density.
The silicon-based active material has a problem in a volume expansion, and in order to solve the problem, a silicon alloy, which finely disperses silicon inside a parent metal, is considered as a technology having the highest probability. The representative silicon-based alloy is disclosed in Korean Patent No. 10-1263265. More particularly, the silicon-based alloy, in which silicon (Si), titanium (Ti), and iron (Fe) are mixed in a ratio of 67%:16.5%:16.5%, 70%:15%:15%, or 74%:13%:13%, is disclosed in the Patent Publication.
Although the silicon-based active material disclosed in the Patent Publication has a relatively large capacity and an improved life characteristic, but according to a rapid increase of the use of mobile devices, such as a mobile phone and a notebook computer, a silicon-based active material, which is capable of further improving a life characteristic of a secondary battery, has been continuously demanded.